Ebola haemorrhagic fever

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(07)61016-2.pdf

Epidemic meningitis, meningococcaemia, and Neisseria meningitidis.

In May 1995, an international team characterized and contained an outbreak of Ebola hemorrhagic fever (EHF) in Kikwit, Democratic Republic of the Congo. Active surveillance was instituted using several methods, including house-to-house search, review of hospital and dispensary logs, interview of health care personnel, retrospective contact tracing, and direct follow-up of suspect cases. In the field, a clinical case was defined as fever and hemorrhagic signs, fever plus contact with a case-patient, or fever plus at least 3 of 10 symptoms. A total of 315 cases of EHF, with an 81% case fatality, were identified, excluding 10 clinical cases with negative laboratory results. The earliest documented case-patient had onset on 6 January, and the last case-patient died on 16 July. Eighty cases (25%) occurred among health care workers. Two individuals may have been the source of infection for >50 cases. The outbreak was terminated by the initiation of barrier-nursing techniques, health education efforts, and rapid identification of cases.

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The Reemergence of Ebola Hemorrhagic Fever, Democratic Republic of the Congo, 1995

Although vaccination has almost eliminated measles in parts of the world, the disease remains a major killer in some high birth rate countries of the Sahel. On the basis of measles dynamics for industrialized countries, high birth rate regions should experience regular annual epidemics. Here, however, we show that measles epidemics in Niger are highly episodic, particularly in the capital Niamey. Models demonstrate that this variability arises from powerful seasonality in transmission-generating high amplitude epidemics-within the chaotic domain of deterministic dynamics. In practice, this leads to frequent stochastic fadeouts, interspersed with irregular, large epidemics. A metapopulation model illustrates how increased vaccine coverage, but still below the local elimination threshold, could lead to increasingly variable major outbreaks in highly seasonally forced contexts. Such erratic dynamics emphasize the importance both of control strategies that address build-up of susceptible individuals and efforts to mitigate the impact of large outbreaks when they occur.

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The dynamics of measles in sub-Saharan Africa

Neisseria meningitidis is one of the leading causes of bacterial meningitis globally and can also cause sepsis, pneumonia, and other manifestations. In countries with high endemic rates, the disease burden places an immense strain on the public health system. The worldwide epidemiology of invasive meningococcal disease (IMD) varies markedly by region and over time. This review summarizes the burden of IMD in different countries and identifies the highest-incidence countries where routine preventive programs against Neisseria meningitidis would be most beneficial in providing protection. Available epidemiological data from the past 20 years in World Health Organization and European Centre for Disease Prevention and Control collections and published articles are included in this review, as well as direct communications with leading experts in the field. Countries were grouped into high-, moderate-, and low-incidence countries. The majority of countries in the high-incidence group are found in the African meningitis belt; many moderate-incidence countries are found in the European and African regions, and Australia, while low-incidence countries include many from Europe and the Americas. Priority countries for vaccine intervention are high- and moderate-incidence countries where vaccine-preventable serogroups predominate. Epidemiological data on burden of IMD are needed in countries where this is not known, particularly in South- East Asia and Eastern Mediterranean regions, so evidence-based decisions about the use of meningococcal vaccines can be made.

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Global epidemiology of invasive meningococcal disease.

Background. The African meningitis belt undergoes recurrent epidemics caused by Neisseria meningitidis serogroup A. During 2002, Burkina Faso documented the first large serogroup W-135 (NmW-135) meningococcal disease epidemic. To understand the emergence of NmW-135, we investigated meningococcal carriage and immunity. Methods. Immediately after Burkina Faso's epidemic, we conducted a cross-sectional survey of meningococcal carriage and seroprevalence in an epidemic and a nonepidemic district. We identified predictors of elevated NmW-135 serum bactericidal activity (SBA), a functional correlate of protection, using multivariate logistic regression. Results. The NmW-135 carriage rate was 25.2% in the epidemic district and 3.4% in the nonepidemic district (P<.0001). Compared with residents of the nonepidemic district, those of the epidemic district had higher geometric mean titers of NmW-135 SBA (P<.0001). NmW-135 SBA titers ≥1:8, an estimated protective threshold, were observed in 60.4% and 34.0% of residents of the epidemic and nonepidemic district, respectively (P = .0002). In a multivariate model, current NmW-135 carriage, age, and residence in the epidemic district were independent predictors of having an NmW-135 SBA titer ≥1:8. Conclusions. Extensive NmW-135 carriage and transmission in the epidemic area caused residents to acquire natural immunity. Serial carriage and seroprevalence surveys could establish the duration of immunity in the population. The persistent circulation of NmW-135 underscores the potential for periodic NmW-135 epidemics in Africa.

Predictors of immunity after a major serogroup W-135 meningococcal disease epidemic, Burkina Faso, 2002.

BACKGROUND Shortly after a measles supplementary immunization activity (SIA) targeting children from 9 months to 14 years of age that achieved high coverage, Burkina Faso had a large, serologically confirmed measles outbreak. To investigate the causes of this first reported failure of a widely successful measles control strategy we conducted a case-control study. METHODS Serologically confirmed measles cases aged > or =9 months at the time of the SIA in 6 heavily affected districts were frequency matched on age to 3 controls recruited from people frequenting health centres in the same districts. RESULTS Between January and July 2002, 1287 measles cases were reported throughout Burkina Faso. Of the 707 cases that were serologically confirmed, 358 (51%) were from 9 months to 14 years of age and 265 (37%) were > or =15 years of age. Among cases and controls from 9 months to 14 years of age significant risk factors for measles were lack of measles vaccination and, in the unvaccinated, recent travel to Cote d'Ivoire. Of the recent measles cases in Cote d'Ivoire 54% were there when exposed to measles. Among adults, risk factors included non-vaccination and the lack of school attendance during childhood. Vaccine effectiveness was estimated to be 98%. CONCLUSIONS Migration of children between Cote d'Ivoire and Burkina Faso played a major role in the failure of the SIA to interrupt measles transmission. Synchronization of measles control activities should be a high priority in countries with regions where much migration occurs.

Migration as a risk factor for measles after a mass vaccination campaign, Burkina Faso, 2002

After the large-scale outbreak of Ebola hemorrhagic fever (EHF) in Bandundu region, Democratic Republic of the Congo, a program was developed to help detect and prevent future outbreaks of EHF in the region. The long-term surveillance and prevention strategy is based on early recognition by physicians, immediate initiation of enhanced barrier-nursing practices, and the use of an immunohistochemical diagnostic test performed on formalin-fixed skin specimens of patients who die of suspected viral hemorrhagic fever. The program was implemented in September 1995 during a 4-day workshop with 28 local physicians representing 17 of 22 health zones in the region. Specimen collection kits were distributed to clinics in participating health zones, and a follow-up evaluation was conducted after 6 months. The use of a formalin-fixed skin specimen for laboratory confirmation of EHF can provide an appropriate method for EHF surveillance when linked with physician training, use of viral hemorrhagic fever isolation precautions, and follow-up investigation.

Long-Term Disease Surveillance in Bandundu Region, Democratic Republic of the Congo: A Model for Early Detection and Prevention of Ebola Hemorrhagic Fever

Burkina Faso conducted mass measles vaccination campaigns among children aged 9 months to 4 years during December 1998 and December 1999. The 1998 campaign was limited to six cities and towns, while the 1999 campaign was nationwide. The last year of explosive measles activity in Burkina Faso was 1996. Measles surveillance data suggest that the 1998 urban campaigns did not significantly impact measles incidence. After the 1999 national campaign, the total case count decreased during 2000 and 2001. However, 68% of measles cases occurred among children aged 5 years or older who were not included in the mass vaccination strategy. During 2000 and 2001, areas with high measles incidence were characterized by low population density and presence of mobile and poor populations. Measles control strategies in Sahelian Africa must balance incomplete impact on virus circulation with cost of more aggressive strategies that include older age groups.

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M. Kader Kondé

Papers

Predictors of immunity after a major serogroup W-135 meningococcal disease epidemic, Burkina Faso, 2002.

Migration as a risk factor for measles after a mass vaccination campaign, Burkina Faso, 2002

Long-Term Disease Surveillance in Bandundu Region, Democratic Republic of the Congo: A Model for Early Detection and Prevention of Ebola Hemorrhagic Fever

Measles Incidence Before and After Mass Vaccination Campaigns in Burkina Faso